Computing Hardware

Computing Hardware

1. Computer Systems

   • A computer system is a collection of parts that work together for a common purpose
   • Computer systems are used in most human activities
   • Because we use computers so much it is very important that they are reliable - computers are so reliable we don't look twice
   • Standards
     • Open standard - Standards that are publicly available - Software developed under the can be modified by users
     • Proprietary standards - owned by a company
     • Standards make sure that new software is as reliable as possible
     • Industry standards - standards agreed across the computing industry
     • De facto standards - Standards that develop through common usage until they become accepted
   • Considerations
     • Ethical - What is right or wrong - Privacy is a big issue
     • Environmental - Energy use and disposal
     • Legal - Defined by laws

2. CPU

   • The Central Processing Unit
   • The CPU is responsible for all the processing for every computer
   • The CPU fetches data from memory and processes it
   • Clock speed is the number of fetch execute cycles in a second - 500Hz = 500 cycles per second
   • The more cache memory the more likely the required data has already been saved in cache and does not need to be fetched from main memory
   • A multi-core processor simply has multiple CPUs working together, they may have their own cache - the computer is able to process more instructions at once so more cores make it faster

3. Binary Logic

   • The memory in a computer uses loads of capacitors and transistors so they use 1s and 0s / On or Off
   • NOT gate
   • AND gate
   • OR gate

4. Memory

   • RAM
     • Random access Memory - is the main memory
     • The more RAM in a computer the more programs it can load at the same time
     • When a program is loaded it is copied from secondary storage into the RAM so the CPU can process that data
     • Data lost when computer turned off
   • ROM
     • Read only memory
     • Retains the information programmed by the manufacturer - non volatile
     • Often stores the boot sequence
   • Virtual memory
     • Needed when RAM can't handle all the demands
     • Is the area of the hard drive that is used for temporary storage of memory
     • HDD gives up storage for memory
   • Cache memory
     • Memory located very close to the CPU
     • Stores data waiting to be processed
   • Flash memory
     • Low cost portable and removable storage device
     • Up to 256GB

5. Input and Output devices

   • Needed to get data in and out a computer
   • Input devices
     • Keyboard - data entry in form of characters
     • Mouse - tracks movement and translates to a pointer on the screen
     • Touchscreen - tracks movement and touches on a screen
     • Microphone - Voice/sound input
     • Camera - Inputs a pixel file
     • Barcode scanner - used in supermarkets
     • RFID reader - Electronic version of a barcode - uses radio frequencies to communicate with a reader
     • Special needs
       • Eye typer - camera that tracks eye movement
       • Voice input
       • Joystick
       • Foot mouse
   • Output Devices
     • Monitor - Visual output
     • Printer
     • Speakers - outputs analogue sound
     • Actuators - can make mechanical movements
     • Special needs
       • Screen readers - eg magnification software
       • Actuators - make physical movement
       • Text-to-speech

6. Secondary storage

   • Needed to store data that doesn't get deleted when computer is powered off
   • Is additional storage facilities added to a computer system to store data and programs when power is off
   • Magnetic hard disks - Uses magnetised platters to store data
     • Moving parts
     • Cheaper
     • Quite big
     • Not portable
     • Slow to access
   • Optical Disks / CD - Uses lasers to read data to a reflective surface
     • Easily break/scratch
     • Not that much capacity
     • Moving parts
     • Cheap
   • Solid state memory - stores data electronically
     • Expensive
     • Fast
     • Uses less power
     • No moving parts
     • Can store many GB

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